dt-bindings: net: broadcom-bluetooth: Add property for autobaud mode

Add property, "brcm,requires-autobaud-mode", to enable autobaud mode
selection.

Some devices (e.g. CYW5557x) require autobaud mode to enable FW loading.
Autobaud mode can also be required on some boards where the controller
device is using a non-standard baud rate when first powered on.

Signed-off-by: Hakan Jansson <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Marcel Holtmann <[e-mail]>

Documentation/devicetree/bindings/net/broadcom-bluetooth.yaml

···
        pcm-sync-mode: slave, master
        pcm-clock-mode: slave, master
 
+  brcm,requires-autobaud-mode:
+    type: boolean
+    description:
+      Set this property if autobaud mode is required. Autobaud mode is required
+      if the device's initial baud rate in normal mode is not supported by the
+      host or if the device requires autobaud mode startup before loading FW.
+
   interrupts:
     items:
       - description: Handle to the line HOST_WAKE used to wake